This invention relates to optical communication systems and more particularly to an optical transceiver array.
Optical couplers are now used to communicate optical signals over short and long distances between, for example, two computers, two circuit boards in one computer, and even two different chips on the same circuit board.
In response, integrated circuit technology that enables bi-directional, high-speed optical rather than electrical interconnections has been developed. This technology allows laser emitters and detectors to be integrated onto a semiconductor substrate, making electrical connection with electronic circuitry previously built on that substrate.
Thus, optical rather than electrical communications between electronic devices is accomplished. An optical transmitter-receiver module typically includes both light emitting devices such as vertical cavity surface emitting lasers (VCSELS) and light detecting devices such as photodiodes. Such a module may include separate chips, or more typically, the VCSELS and the photodiodes are grown on the same substrate. See U.S. Pat. No. 5,978,401 incorporated herein by this reference.
Driver-receiver circuitry modules, typically in the form of ASIC chips, include driver circuitry which receives electrical signals from one electronic device and which, in response, drives the VCSELS accordingly. The ASIC also include receiver circuitry for receiving signals from the photodiodes and, in response, which processes those electrical signals providing an appropriate output to the associated electronic device.
The combination of the VCSELS and the photodiodes and the ASIC circuitry is typically called an optical transceiver. One way to hybridize the VCSELS and the photodiodes and the ASIC receiver circuitry is by xe2x80x9cflip-chip bonding.xe2x80x9d See U.S. Pat. No. 5,858,814, incorporated herein by this reference.
However, one problem that occurs during the manufacture of such transceiver arrays is the presence of contaminants on the surfaces of the photonic devices throughout the manufacturing process. The presence of such contaminants may reduce the optical transfer efficiency or even result in failure of a photonic device to transmit or receive light entirely.
It is therefore an object of this invention to provide an improved method of integration of integrated circuits.
It is a further object of this invention to provide such an improved method which reduces or eliminates contamination of the surfaces of the photonic devices.
This invention results from the realization that a more optically efficient interdigitated transceiver array is achieved from the use of multiple etch stop layers to provide optically clean surfaces on all of the photonic devices.
The present invention provides a method of making a hybrid interdigitated device while protecting the surfaces of the photonic devices. The primary steps are hybridizing first and second substrates, the second substrate including at least one first type photonic device, the epitaxial layer construction of the first type photonic device including at least first and second sacrificial layers. A first flowable hardenable material is applied to join the first and second substrates, then the material is cured. The second substrate is removed as is the sacrificial device and the first sacrificial layer. Then a third substrate is hybridized with the first substrate, the third substrate including at least one second type photonic device and at least a third sacrificial layer in the epitaxial layer construction. The method also includes introducing a second flowable hardenable material to join the first and third substrates; curing the second flowable hardenable material; removing the third substrate as well as the second and third sacrificial layers.
The first substrate may be a silicon CMOS substrate. The second and third substrates may be chosen from the III-V group of materials and are preferably GaAs. The sacrificial layers may be AlGaAs with a 30% Al content.